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Medical talk Most people overestimate the benefits and underestimate the harms of medical tests and treatments, according to a new review of existing medical studies.

"What struck us is that, in general, people thought that treatments were going to be much more beneficial to them [than the evidence suggested]," says researcher Professor Chris del Mar of Bond University.

"And that the harms would be much less," says del Mar.

He says clinicians and patients need to make decisions based on more accurate information on the pros and cons of such interventions.

"This is one of the most important ways we can save the healthcare system from going bust."

Assumptions

Del Mar suggests this optimistic bias in patients could be partly due to the widespread assumption that more tests and treatments mean better healthcare.

"We know it's very difficult for doctors not to do something," he says.

This is especially the case if a patient asks for a procedure, believing it will work.

This practice is reinforced when people feel better after the treatment -- probably because of placebo, says Del Mar.

The most extreme overestimate of benefits occurred with cancer screening, where there was an order of magnitude difference between the actual benefit and what people thought it was.

Related to this is an overestimate of the risk presented by some cancers. For example, some studies found women overestimate their risk of breast and cervical cancer as well as the effectiveness of screening.

Del Mar says this was likely due to "in-your-face" public awareness campaigns on TV and the use of relative rather than absolute risk estimates when explaining the number of lives saved by interventions such as screening.

"In fact the odds are you're not going to die of breast cancer," says del Mar.

However, when it comes to treatment for diseases like cancer, there are particular challenges because people need hope they can do something.

But, del Mar says, it is imperative that people know the facts on what is known about the risks and benefits of any given treatment or test before they decide if they want to proceed.

"It depends on the values of the patient. You can't apply evidence without factoring in patient values," he says.

Myths

Del Mar says some people argue that more talk will lead to longer consultations but he says studies show this is a "myth".

"You can do it all in the same time frame. All you're doing is exchanging one kind of discourse with another," he says.

"It does require a change in mindset."

In fact, evidence suggests more talk results in less intervention, says del Mar, citing the case of PSA testing.

"If you talk to people first before you do the screening, and explain all the downstream consequences of being screened, a lot of men say they don't want it," he says.

While unnecessary or unwanted treatment and tests add to the cost of healthcare, del Mar says "overtreatment" can also result in physical and emotional harms.

"I think [more talking] will save money but I don't think that's the main driver. The main driver is delivering better care," he says.

Del Mar also dismisses the idea that recommending interventions is the best way for doctors to avoid being sued by patients.

Instead, he says it is far more defensive for them to give an accurate picture of what is known about the pros and cons of different options.